Many electronic devices, such as smart watches, smart telephones, laptop computers, and tablet computing devices include a capability to sense a force or a touch provided by a user. Input force, typically as part of a graphical user interface (GUI), can enable a variety of functionalities, such as providing differing device response for given threshold levels of user input. That is, a relatively lighter user input force may result in a first device response, while a relatively stronger or higher magnitude input force may result in a second device response. Conventional force and touch sensing systems may be performance limited in accuracy or resolution, and can require relatively high-cost components demanding significant power.
A capacitive-based force sensing system, used in many electronic devices, is illustrative of the limitations imposed by typical input force sensing systems. A pair of electrically charged capacitive elements, such as plates, are separated by a dielectric medium and electrically connected to allow monitoring of capacitance, a value that changes with separation distance between the capacitive elements. The change in capacitance is calibrated with applied force to provide input force sensing. Such systems can present operational drawbacks, such as relatively high power demands caused by the need to maintain a constant charge on the capacitive elements. However, a system that employs micro electro-mechanical elements in concert with pressure sensing may provide an input force sensor with improved performance characteristics, such as reduced power requirements, and reduced complexity and part-count, thereby increasing reliability and reducing cost.